<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
   <script>
       var a = true;
       var b = false;
       var c = true;
       var d = false;
       console.log("a && b : "+ (a && b));
       console.log("a && c : "+ (a && c));

       console.log("a || b : "+ (a || b));
       console.log("b || d : "+ (b || d));

       console.log("!a : "+ (!a));
   </script>
</body>
</html>